


A Measure of Luminosity

by evadne



Series: Names for the Galaxy [2]
Category: Sherlock (TV)
Genre: Alternate Universe - Science Fiction, M/M, PWP, Writing on Skin
Language: English
Status: Completed
Published: 2015-02-21
Updated: 2015-02-21
Packaged: 2018-03-14 00:32:39
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,792
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3401903
Author URL: https://archiveofourown.org/users/evadne/pseuds/evadne
Summary: <blockquote class="userstuff">
              <p>A coda to <i>Names for the Galaxy</i>. Stars, spaceships, language lessons and sex.</p>
            </blockquote>





	A Measure of Luminosity

**Author's Note:**

  * For [alltoseek](https://archiveofourown.org/users/alltoseek/gifts).



> This is 100% [alltoseek's fault](http://parachute-silks.livejournal.com/46027.html?thread=375499#t375499) . It is also 100% porn*, with no redeeming features whatsoever.
> 
> *OK, it's actually more like 80% porn. The rest is fluff and spaceships.

‘It isn’t the texture,’ John decides, although it could be, because the texture is gunpowder and silk, rough on the backs of his hands and insufferably soft on his thighs. But it isn’t the texture.

 

‘Do you remember before,’ he says, ‘when I told you I wanted all of you?’ Before: one planet at a time before, incompleteness – he’s fraying apart as the maddening textures draw nearer and nearer – ‘That’s it, that’s why –‘

 

And Sherlock says he knows, and his higher arms cradle themselves around John while the lower ones dip and dip and the brush trails along his cock and it’s language too sharp for his body to bear, too good to ever think of stopping.

 

Sherlock asks him why he always dreams about the sky and John gasps, gasps in answer because his tongue’s damp with need and a thousand miles away from the nearest English word and clouds reel and roil up above and tender bristles graze the slit, the head, oh God please, Sherlock, please –

 

He wakes to warmth, plants, and gently dawning artificial sunlight, as he has done for the past six weeks.

 

Things occur to John in slow, bleary sequence. He notices first that his pyjama bottoms are damp and clinging to his cock, and he’s still hard: the dream (oh, _Christ,_ the dream) he’s just stumbled out of didn’t make him come in his sleep, then, but he’s clearly been leaking like hell. Not…enormously surprising, really, when he remembers – no, not now, or he’ll never get out of bed. But fuck, he hasn’t had a dream that vivid in months, and then they were usually nightmares. This was…decidedly not a nightmare.

 

The second thing John notices is that while warm, he isn’t suffocatingly hot or struggling to breathe through a noseful of hair. This is unusual enough that he opens his eyes.

 

‘Oh fuck,’ he says.

 

Sherlock attempts to grin at him, or at least John thinks that’s what he’s doing, but his mouth is open and his breath is coming in quick pants and a grin seems beyond his abilities. This is because he has four fingers buried in his left slit and is shoving them in and out with no finesse whatsoever. John almost never fucks him this hard, unwilling to risk doing damage to biology that still holds mysteries for him, but yeah, OK, he thinks about it, and he knows Sherlock thinks about it too but seeing it…

 

‘Can I –‘ John says, voice coming fast and strained, and Sherlock gasps ‘Yes’, and John presses a fingertip to Sherlock’s right side and strokes it slowly across the line there. They know now that dual stimulation is not part of conventional sex for Gliesans, and that when John touches both slits at once he’s engaging in something that would be considered hardcore kink on Gliese, and too intense for most people to cope with. So no surprise then that Sherlock loves it more than almost anything else.

 

Sherlock whimpers, tries to speak but can’t. He drops his free hand into the pot of ink they keep by the bed and trails patterns over John’s stomach, arms, back as John crouches over him, stroking the right slit with cruel slowness while Sherlock pumps rapidly at the left one. The asymmetry of pace is getting to him, John can see, the conflicting signals ratcheting up the tension. He could keep Sherlock on the edge like this for a while, he thinks, the rough and the measured, the too much and the not enough. But Sherlock is making low noises that sound like they’re being dragged out of his throat and John wants to see him come. So he lifts his hand away (and the sound Sherlock makes at that is higher, and his fingers on John’s skin skitter before digging in, nails pressing the ink in sharply) and says, ‘Come on, that’s it, God you have no idea how hot this is –‘ and Sherlock throws his head back and moves his hand faster before suddenly withdrawing it, body tensing as the left slit closes rapidly. Another thing John knows now is that if he rubs the closed slit it sends tremors through Sherlock’s body and makes his orgasm last for minutes, and so John presses his thumb to it and rolls it round and round, drawing shock after shock through Sherlock until he slumps limply to the bed.

 

The right slit is still wide open and drawing John’s eye with its needy pulsing, but that can wait. He drapes himself over Sherlock and says, ‘Morning.’

 

He doesn’t expect a reply: talking will be a problem for Sherlock for a few more minutes. But he feels Sherlock’s fingers spiral across his back, and knows he’s being talked to, whether he can hear it or not. He smiles into Sherlock’s neck, and Sherlock grins back at him. When John thinks there’s a chance of getting a verbal answer, he says, ‘So what brought that on? Not that I’m complaining. I’m really, really not complaining. But I’ve never woken up to you doing _that_ before.’

 

‘Well, I’ve never woken to you bucking your hips and mumbling my name in your sleep before,’ Sherlock says. ‘It…necessitated a response.’

 

‘Ah,’ John says, hardening a little bit further at that thought, Sherlock _watching_ him and getting off on it.

 

‘What happened in the dream?’ Sherlock says, and John feels himself flushing instantly.

 

‘You,’ he begins, swallows, and then says hurriedly, ‘You had your lower arms back, and you were…’

 

‘Oh,’ Sherlock says. ‘Interesting.’

 

‘I know you don’t want them,’ John says, hurriedly. ‘I remember what you said, about memories carried in the body and what you’ve done with the arms you have now and how this body is yours now. I just…’ He struggles to remember what he said in the dream; he remembers talking, and he feels like it was important. Then again, if it’s really important the words he needs will turn up eventually.

 

‘You like the idea of it,’ Sherlock says, thoughtfully. ‘Hm. So tell me, what was I doing with them?’ His hand slips under the covers and cups lightly over John’s cock through his pyjamas. ‘Let’s see, what _would_ I do with them? Well, write on you, obviously, more precisely than I can with my current fingers.’ He rubs lightly through the pyjama bottoms and John holds very still and remembers to breathe, and Sherlock says, ‘I’d run them down your neck and the cold of the ink would make you shiver and you’d tilt up your head to give me better access. I’d drag them over your nipples, stain them, and they’d peak up against the rough glide of it.’

 

His mouth trails his words, on John’s neck and then his chest moments after John imagines brushes there. John is breathing heavily now, and breathing can only get more difficult as Sherlock yanks down his pyjama bottoms and kicks them away. John sleeps shirtless, because it’s warm in the suite and Sherlock likes to sleep in contact with as much of John’s skin as possible, so he’s naked now and Sherlock shoves the duvet off the bed and puts his face near John’s cock so that John feels his breath as he says: ‘I’d run them in spirals down the outside of your legs and then in square spirals up the inside. Night blue and wallpaper green, you don’t know what that signifies but I’d tell you, when my mouth was free. Which wouldn’t be for a while, because…’ He kisses John’s shoulders, his scarred leg. ‘Because?’ John gasps.

 

‘Well, I’d be kissing you, of course,’ Sherlock says. ‘Kissing you while I put my non-brush fingers around your cock and splayed them out, and I’d stroke you like that with one hand while stroking the spaces between my fingers with the brush. Your body wouldn’t know what to make of it, it would be like with me, earlier, too much stimulation but you’d only want more of it. And then –‘ He wraps his hand around John’s cock and begins moving it methodically. John squeezes his eyes shut. ‘Then,’ Sherlock says, ‘I’d take my hands away and take you into my mouth and you’d –‘ His hand speeds up. ‘You’d grab my arms and press the bristles into my side, make me stroke myself with them while I sucked you –‘ and what he’s saying is hot but the fact that he can barely get the words out anymore, that liquid is dribbling insistently from his right slit as he talks, that’s hotter still, and John’s hips begin thrusting involuntarily into Sherlock’s fist. ‘And we’d both come like that,’ Sherlock says, ‘me from my own hands scraping bristles against me and the odd bristle slipping inside and rubbing there, you from my mouth, all over me –‘ and John groans loud enough to wake the ship and does just that, coming all over Sherlock’s hand and his own stomach and the bed. And Sherlock’s moaning and rubbing frantically at his side until liquid floods his fingers and he collapses on top of John.

 

‘Oh my God,’ John says, once words become an option. He pulls Sherlock close. ‘Fucking hell.’

 

Sherlock curls up in order to maximise the amount of his body directly in contact with John and grins against John’s skin. John swears he can tell by the feel of the grin that it’s a particularly self-satisfied one. ‘Yeah, all right, I might have a bit of a kink,’ he says. He pauses. ‘That doesn’t…does that bother you? I’d understand if it did.’ John’s thoughts, after all, stray close to sex as Gliesans typically experience it: dipping paintbrush fingers into one’s own left slit and then bringing them to a lover’s right, or vice versa, is, apparently, how sex normally works for them. He isn’t sure what Sherlock will think of John fantasising about something that could be regarded as an analogue to that.

 

‘Did it look like it bothered me?’ Sherlock mumbles, words coming back to him again. ‘I mean, I suppose it depends on how broadly you define the word _bothered._ I’m certainly not…indifferent to the idea.’

 

John parses this. ‘You like it?’ he says.

 

‘Again,’ Sherlock says, ‘I thought I’d made that fairly obvious.’

 

That, in turn, is arousing. If they keep talking, John thinks, they’re going to have to have sex again, and appealing as that idea is they really need to get up at some point. So instead of replying, he lifts his arms to examine the ink patterns there. ‘You going to tell me about these?’ he says.

 

‘In a bit,’ Sherlock says. ‘I’d have to get off you to reach some of them, and I’m not ready to do that yet.’

 

John grins, and twirls a strand of Sherlock’s hair absently about his fingers. ‘I came over some of it,’ he observes. That’s starting to feel unpleasant, drying on his skin, but he isn’t ready to move yet either.

 

‘I knew you would,’ Sherlock says, sounding vaguely embarrassed. ‘I chose what to write there with that in mind.’

 

_Oh._ That’s…very interesting. John decides he needs to get up before he loses all willpower to do so. Sherlock grumbles when he starts to move, but eventually slides off him. John picks up the duvet from the floor and covers Sherlock. He’s heard the Norwegian ships have perfectly temperature controlled suites, such that no duvet covers are necessary, but he thinks he’d miss it, himself. Even if waking up every morning with Sherlock plastered all over him and the duvet on top of them both is going to lead to him fainting from excessive heat one of these days.

 

The suite is utilitarian, but they’ve made it their own. They’ve stuck wallpaper identical to the kind they have at home over the inside of the cupboards, and John’s pretty sure they’re the only suite in the ship to have a tiny lab in one corner or an experiments fridge. The dark metal of the ship curves over them, barely visible amidst the carefully controlled network of vines that coats almost every room. The metal was gleaming at first before discolouring rapidly, so that now it’s dull in places and bright in others, and a mess of colours. Often these colours seem to find their way into the images Sherlock paints on John. One day John will ask what that means, but he’ll give Sherlock time to work it out himself, first. The things he says that way sometimes come from places too deep for him to have looked at closely.

 

Sherlock gets up as John’s rummaging in the shelves, and comes up behind him. He runs his hands over John’s arms, and begins talking. ‘This, deeper colour shading out to pastels, is – it’s something people do when they’re having trouble expressing themselves. If it’s all fairly pale and quite a small shape, it’s just the equivalent of saying _um,_ really. Big, dark ones like this indicate…cognitive overload, I suppose. It’s difficult to explain.’

 

He says _it’s difficult to explain_ without the anxiety that accompanied statements like that when they first started doing this. They both know now that they’ll be able to work it out eventually, or if not, well, perhaps John understands enough, anyway.

 

‘You did some on my back this time,’ John says, dropping his clothes on the bed and resisting the urge to turn round into Sherlock’s arms. ‘We’ll have to use a mirror.’ He pauses. ‘I thought writing stuff on people where they can’t see it indicates aggression.’

 

‘You’re always oversimplifying it,’ Sherlock says, but without rancour. John opens the suite controller on his handchip and taps the button to turn the cupboard doors into a mirror. He turns side on, and can just see the doorways Sherlock’s painted on his back, each one full of stars and covered by a fine network of frantically zigzagging and swirling dark green lines. He finds the place where Sherlock dug his nails in, and wonders how long it’ll take before the ink there fades. He hopes it’s a while, and he suspects Sherlock does too, because Sherlock’s fingers follow John’s there and linger.

 

‘I’m not sure about these yet,’ Sherlock admits.

 

‘You’ll tell me when you can,’ John says, and then reluctantly steps away. ‘I’m on patrol from seven,’ he says. ‘Got to shower. And _no_ , we’re not showering together, last time we tried that we didn’t manage to get out for forty minutes and we used up all the water for our wing, if you remember.’

 

‘I don’t see the point of the patrols,’ Sherlock complains, draping himself over John’s back as inconveniently as possible. ‘We haven’t been attacked once, by anything, in the entire time we’ve been out here.’

 

‘For all we know, Moriarty’s found an inhabited planet and made himself king of it and is on his way with an army,’ John retorts. ‘And don’t tell me my job’s pointless.’

 

‘Fine, it’s not pointless, I just think there are better uses for your time.’

 

‘I don’t exist to run around after you,’ John says, but without venom. They’ve had this argument for real before, early on in their time on the spaceship, in the first shock of Sherlock’s adjustment to John’s world _not_ revolving around him. But it’s got easier since then, and now John’s confident that they’re only playing at it, and that when he leaves Sherlock will just roll his eyes and get on with his day. When John’s patrol ends at twelve he’ll come back and find out if Lestrade’s got a case, then they’ll race about till John realises Sherlock hasn’t eaten a thing all day and drag him to the nearest dispenser, and they’ll climb up to one of the viewpoint chambers and eat while watching the distant stars drift by. John may or may not get to tackle a would-be murder to the ground, and Sherlock may or may not attempt to have sex with him in the engine room again.

 

‘You’re grinning,’ Sherlock says, fingers creeping round John’s jaw and feeling for his mouth, ‘why are you grinning?’

 

‘Because I’m happy,’ John says, and smiles wider at Sherlock always missing the obvious, and then wider still as Sherlock’s hands stroke the corners of John’s mouth as though communicating directly with the smile. He dodges out of Sherlock’s affectionate imprisonment, kisses him as quickly as possible to avoid being captured again, and darts into the bathroom, still grinning.

 

*

 

The next few days pass quietly, or their version of quietly, at any rate. Sarah Sawyer, the head mechanic, reports a spate of energy thefts, and they spend hours on stakeout which finally culminates in the perpetrator making the suicidal decision to escape by stealing a spaceskin and fleeing through the airlock. John and Sherlock follow him less to bring him to justice than to save his life, and drag him back to the ship. It’s frighteningly still outside, and more beautiful than John can take in; he’s sorry to have to come back so soon.

 

‘Another time,’ Sherlock says, ‘we’ll borrow skins ourselves and slip out when no one’s paying attention, and spend as much time out there as we want.’

 

‘We shouldn’t,’ John says, but Sherlock just laughs; they both know that John will go along with it, and love every minute.

 

Then they head back to their suite, and the atmosphere between them becomes slightly more charged, because they’re both familiar now with their mutual reaction to adrenaline. John kisses Sherlock hard as soon as they get through the door, and Sherlock kisses back at first, but then he pulls back and says, ‘Could we – I want to try something.’

 

He crosses to the cupboard and reaches under a pile of clothes to withdraw a slim wooden box. He opens this to reveal brushes, and John goes still.

 

‘I want you to write on me,’ Sherlock says. ‘Or draw, anything. And I…I thought…’ He turns back to the cupboard and busies himself doing something, and when he turns back John draws in breath: he’s attached short brushes to each of the fingers on his right hand. John can’t see how they’re attached, but there’s nothing visible so it’s probably through some kind of clingfield, and Sherlock flexes his fingers to demonstrate the control he has over the brushes.

 

‘You’ve been practising,’ John breathes. ‘You’ve been thinking about this.’ And then he doesn’t want to talk any more, not with his mouth; he takes a brush from the box and opens the lid of the hollow in the desk where they keep the pots of ink. ‘ _Please_ get your clothes off,’ he tells Sherlock, but Sherlock’s already shedding them before John even gets all the words out, and when John gestures wordlessly to the bed Sherlock stretches out on it and John’s mouth is dry with wanting.

 

He arranges the pots of ink unsteadily along the edge of the bed; they’ll likely spill but he doesn’t, can’t care about that right now. He dips the brush into the black ink and begins a careful progress up Sherlock’s leg, towards his knee. He tries not to make himself focus too much on the detail of the movement, to call up feelings instead. _Starline or spectral fields_ becomes a deep pool of ink near Sherlock’s ankle, the beating pulse of John’s heart after a chase away from a balcony feathers out into curling leaves. _I love you_ coils out of sight as a single dot behind Sherlock’s knee (Sherlock tenses, breathes _it tickles_ , and John moves higher, higher, the line soaring up Sherlock’s thigh).

 

Then he feels brushes on his shoulder and twists his head till he can just see them scrape pale blue down his arm, so hard as to be almost painful; a dark red follows in between. They struggle with colour vocabulary, because two shades a handful of hex codes apart can be wildly different to Sherlock but human attempts to distinguish them with words – carmine, scarlet, post box, wine – ring false to him, the associations hanging off the words all wrong. John doesn’t know what the dark red means, or what the very slightly lighter red that Sherlock uses next does. But he knows the care Sherlock takes painting down John’s body, the soft, intent precision of the brushes on John’s neck, is as intimate as anything he can imagine.

 

He leans lower, enough to breathe into Sherlock’s mouth, and John’s arm is beginning to ache from holding himself over Sherlock while his other arm takes the brush where instinct dictates, but he doesn’t care. He’s switched colours at some point, and he’s barely learning what they mean in Gliesan and will never be able to perceive their gradations the way Sherlock does, but Sherlock knows he’s trying, and when John attempts bits of Gliesan the corner of his mouth quirks up and then rapidly smoothes again the way it does when he’s taken by surprise by his own happiness. So John attempts _Fantastic,_ the closest equivalent of which is an image of something striking and lovely (John generally paints stars and fire) scattered with rapidly jabbed dots. Sherlock looks at it emerging over his chest and makes breathy sounds as it begins to materialise. John doesn’t know if it’s the sensation of fine brush tip against his skin or the meaning making its way into his pores that does it. He doesn’t know what’s behind his own reactions either, the way the brushes now curling near his belly button, now gliding round and up towards his back make the skin they touch tingle, key him up further and further. He hopes they can do this again and again till it’s routine, till they both understand exactly what it means to them, what it does to them and why.

 

The side of the brush flicks past the base of John’s cock, bristles catching slightly and John’s arm gives out. He finds himself on top of Sherlock, and it would be an absurdity not to kiss him when their mouths are so near so he does, and feels the brushes on Sherlock’s fingers close in on his cock. In response he reaches blindly for the box, left by Sherlock near the bed, and manages to fumble for another brush. Then he dips it in ink, he doesn’t even know what colour, and runs the two brushes down Sherlock’s sides simultaneously, speeding up as he approaches the slits. They’re half open, narrow slots just wide enough for the bristles to drag inside them and chafe very slightly at their sensitive inner sides as John pulls the brushes along. Sherlock whines desperately at that and his free hand grabs John’s shoulder and squeezes it, but his other hand continues to tease, the endless up-and-down dance of the brushes with no relief.

 

John slides the tip of one brush into the right slit and probes it gently. It’s shallower than the left and the brush fills it almost entirely. As the slit quivers, faster and faster now, the movement makes the brush rub up against its sides and John’s shoulder stings with the bite of Sherlock’s nails. ‘Tell me if it’s close,’ John says. ‘I want you to come both at once.’ Sherlock groans, his head tipped back into the bed, but manages a nod.

 

John drops the second brush and bends to put his mouth to the left slit instead, while slowly pulling the brush out of the right, leaving a trail of prickling contact that must be on the verge of uncomfortable, but Sherlock isn’t objecting, anything but. Then he pushes the brush back in while pushing his tongue as far into the left side as he can. It’s too deep for it to reach all the way in, but it slides against the inner walls, and John’s learned that flicking it from side to side draws lovely high noises from Sherlock and makes his heels dig hard into the bed. Doing it while working the other slit with the brush proves more dramatic; John’s fairly sure his shoulder is bleeding now and the noises are coming from Sherlock in a constant stream. If he doesn’t come soon John will have to stop before he passes out from lack of air.

 

‘God you’re amazing,’ John says, lifting his head, and: ‘Going to make you come,’ and _he_ wants to come almost more than he can stand but he wants to see Sherlock get there first, wants to see the liquid soak the brush.

 

Sherlock’s hand detaches itself from John’s shoulder and makes its way unsteadily down, at which point one finger runs up the underside of John’s cock to meet where the brushes are twirling round it and press at the meeting point. ‘Please,’ John says, and Sherlock says, ‘In me,’ with enormous effort, John knows how much he must want it to force the words out when he’s so overstimulated and so close and fuck, that’s – John flops to one side and then manages to get upright enough to press the tip of his cock into the left slit, which sucks him in greedily. He can’t get much in, although he has thoughts about trying, about gently stretching the slit with his fingers and seeing how much of his cock he could push in. Sherlock would want it, is always trying to get John pressing in further, trying to take in more of him. John won’t hurt him for anything, but if they were careful…for now, though, it’s just the head, enveloped in slick heat, and Sherlock’s hand comes up to make a fist for the rest of John’s cock to glide through as John moves in and out of the left slit with as much care as he can manage while swirling the brush round and round in the right.

 

When Sherlock comes, it’s incandescent. John’s done his best to pace his movements to make him come both sides at once, something they rarely have the patience and concentration for but is explosive whenever it happens, and this exceeds all previous attempts. Liquid _pours_ from the right slit and doesn’t stop for what feels like an impossibly long time; tremors rack Sherlock’s body and the left slit clutches frantically at John’s cock again and again, all but milking it until John’s orgasm is torn from him too, pulling with it a string of noises he didn’t even know he was capable of.

 

They lie there, covered in sweat and come and smudged ink, for some time. John has no idea how long; he’d be lucky to remember his own name, at this point. He holds Sherlock close, loving the clash of the colours on their bodies, the cacophony of pattern.

 

‘We can do that again,’ Sherlock says, at last. His voice is _wrecked._ There is no way John’s getting hard again any time soon, but the sound of it makes him shiver anyhow.

 

‘We definitely can,’ John agrees, and warmth curls in him at the thought. It’s thrilling, still, to find new ways to talk to Sherlock, new paths into the history John still barely knows and the pathways of his mind John may never truly understand. And to do that while having some of the best sex of his life is…well. It’s a continuing shock that he’s here, that he’s allowed to have this. He never knew he had such capacity for happiness, thought he was built for adrenaline and excitement and controlled fear. But perhaps he can have all of those things and have, too, the sheer joy of Sherlock Holmes in bed with him, the messages John left for him blurring into the ones he left for John.

 

John gets to do this, to make Sherlock feel so much, feel so good that his brain whirls in and in to this one point, one place and time, one sharp sensation. It won’t last: Lestrade will message, and Sherlock’s eyes will snap open. He’ll read the message and a fierce light will come into his eyes. _Idiots_ , he’ll say, or: _If his uncle has a bicycle, then –_ and leap out of bed. John will get to see that transformation too, the minute to minute lightning changes, all the things Sherlock can be, his brilliance and his affection and his pleasure.

 

‘You’re grinning again,’ Sherlock says. ‘Should I ask why?’

 

‘You know why,’ John says, closing his eyes and curling closer.

 

He feels Sherlock lift John’s arm and pull it further over himself, tugging them closer still. Then a soft kiss to the back of his head, and the shape of a smile. ‘Yes,’ Sherlock says, ‘I suppose I do.’


End file.
